#Quercus marilandica.#--Black Jack oak is localized in four small compact groves on the Reservation. These sites, though well separated, are similar. All are on steep lower slopes, where there is dry rocky clay soil and the exposure is mainly south. Probably all four groves date back to the time when the area was still in an undisturbed state. Originally they were perhaps largely separated from the remainder of the woodland. Black Jack oak is more tolerant of heat and drought than most of the other hardwoods are. The species is intolerant of fire, but perhaps was partly protected under original conditions by the sparseness of herbaceous vegetation on the poor soil where the groves were situated. These oaks are relatively slow-growing. One stump of 9-inch diameter, typical of the larger Black Jack trees, had approximately 60 annual rings. Under present conditions there is little or no reproduction and these trees are dying out as a result of competition by other hardwoods. Under protection from fire and browsing, elms, other oaks, locust and dogwood have closed in about the groves and seem to be shading them out. There are several mature oaks of anomalous appearance, in different places within a few hundred feet at most of the groves of Black Jack. Most of these appear to be hybrids between the present species and _Q. velutina_, as they are somewhat intermediate in size, bark texture, and leaves. This oak produces a mast crop used by various birds and mammals, and groves are frequented by blue jays, fox squirrels, white-footed mice and woodrats. In the mid-forties when the woodrat population was high, there were many of the rats' stick houses in the groves, built either at the bases of the trunks or among the dense branchlets in tops of fallen trees. By 1952 the population of woodrats was much reduced and had disappeared entirely from these groves. The houses were collapsed and decaying. Horned owls (_Bubo virginianus_) and barred owls often make their day roosts among the dense interlacing twigs of these trees, and red-tailed hawks have been known to roost for the night in the same kinds of situations.